I know that when you install hardwood flooring, you need to leave a small expansion gap along the walls. I understand that this is to allow the wood some space to move when the wood expands due to humidity and temperature fluctuations.
My question is why the expansion gap works, especially with floors that are nailed or stapled to the subfloor. If each board is nailed down, how is an expansion gap along the edges of the room going to help when the wood expands? Wouldn't each board just collide into the ones alongside it?
Plus, even if you have a floating floor where most of the boards are not nailed down, the ones along the edge of the room typically would be nailed...so wouldn't they be immobile and prevent any movement into the expansion gaps?